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Working on a car where the owner wants to convert from 6V to 12V. But it is a bigger issue than that. He dropped a Chevy 350 into the car. This brings up a new issue. The '48 was Positive Ground. Can I keep it this way, or will it now need to be Negative Ground. If I need to convert to Negative Ground, what do I need to do so I don't 'fry' anything?

I don't know much about Chevy engines but what that needs for the ignition would decide the change. Most likely if the GM electronic, then neg ground. Just going from positive to negative ground, nothing else in a stock car needs to change other than repolarizing the generator. If you already have a 12v generator/regulator setup that would need to repolarize. A proper alternator would need to go in if you went that route.

Going to 12v would have already necessitated most of the other changes such as bulb and instrument changes.

Not sure what you are doing about the high current 6v heater blower(s) and radio so that has to be determined. Blower is OK with either polarity. If the stock radio stays 6v with the arrangement, then if it has had the vibrator replaced with solid state that would need to change to a negative ground version.

You might investigate the 12 to 6v reducer/regulator setup for the heater(s) and other items. If you go that route, depending on what you add the 20amp may be a better choice.

OK, I need some validation.

I created 2 wire lists. The first one (entitled 48 Packard 6V)shows every wire that has anything to do with the '48 Packard engine.

The second one (entitled 48 Packard 12V Chevy 350)shows the '48 with the Chevy 350 wiring. I need to know if I show all of the wires correctly on the second one.

Please take a good look and either let me know if I have it right, or what (if anything) I missed or need to change.

Thank you so much!

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Guess I'm blind but don't see any difference between the two drawings. One wire missing is the main cable between battery + and starter. Another is the starter circuit you asked about.

A couple of other things come to mind.

With the reversed polarity the ammeter connections will need to swap + to -.

If you are using the stock Packard gauges they will require the proper 6 volts feeding them as well as the stock Packard senders. I don't know how Chevy senders mount but those particular Packard senders used on 22-23 series cars are larger than average.

The oil sender may not be an issue since it can be plumbed in where space is available but the temp sender may be. It needs to be fully covered with coolant -- preferably freely circulating coolant in the block -- so it can get a proper sampling. Since it is long and wide that may be a real issue on the Chevy. Just be aware that the reading may be false if too much plumbing ingenuity is required and coolant flow around the sensor is marginal or has a chance to cool down.

Thanks Howard. HAHA! I posted the same photo twice. I am going to repost in the main thread with both diagrams (different this time).

Thanks again Howard. Funny thing is, the Temp Sender is the same between the two engines! I took the one out of the '48 Packard and it fit the Chevy perfectly. And there is good coolant flow around the sensor.

The Oil I have not figured out yet.

As for everything else that need to remain 6V, I am installing a step-down transformer for those.

As for everything else that need to remain 6V, I am installing a step-down transformer for those.

Hope you mean resistor or regulator. Transformers won't work on DC voltage.

Good to know the sender will work. One of the guys here on the forum had issues installing his pre 51 sender in a 53 Packard engine because the later senders are much smaller.